I found it in backups from ITS. ITS is the MIT operating system for the PDP-10, which was the workhorse around the AI Lab, Logo Lab, Lab for Computer Science, Mathlab, Dynamic Modeling group, etc.

Hmmm, I’m vaguely remembering uploading the TI-Logo source to the MIT ITS PDP-10 for backup purposes too. If so it might be there also. You’d want to be careful about the copyright on that. Though I’d love to see it again

That's why I try to run most of the finds by the original authors. I sent you an email with some more details; or at least I tried and it didn't bounce.